Written by Karen C. Fox
NASA Goddard Space Flight Center
Greenbelt, MD – The sun emitted a significant solar flare, peaking at 2:14pm EDT on October 20th, 2012. This flare is classified as an M9 flare. M-class flares are the weakest flares that can still cause some space weather effects near Earth.
Since flares are rated on a scale from 1 to 10, an M9 is a particularly strong M class flare, but still ten times weaker than the most powerful flares, which are labeled X-class.
The flare appeared on the left limb of the sun, from a region that is just rotating into Earth’s view.
Solar flares are gigantic bursts of radiation. The harmful radiation from a flare cannot pass through Earth’s atmosphere to physically affect humans on the ground, however — when intense enough — they can disturb the atmosphere in the layer where GPS and communications signals travel. This disrupts the radio signals for as long as the flare is ongoing, anywhere from minutes to hours.
The National Oceanic and Atmospheric Association, which is the United States government’s official source for space weather forecasts, categorized the radio blackout associated with this flare as an R2, on a scale from R1 to R5. It has since subsided.
Increased numbers of flares are quite common at the moment, since the sun’s normal 11-year activity cycle is ramping up toward solar maximum, which is expected in 2013. Humans have tracked this solar cycle continuously since it was discovered in 1843, and it is normal for there to be many flares a day during the sun’s peak activity.
What is a solar flare?
A solar flare is an intense burst of radiation coming from the release of magnetic energy associated with sunspots. Flares are our solar system’s largest explosive events. They are seen as bright areas on the sun and they can last from minutes to hours. We typically see a solar flare by the photons (or light) it releases, at most every wavelength of the spectrum.
The primary ways we monitor flares are in x-rays and optical light. Flares are also sites where particles (electrons, protons, and heavier particles) are accelerated.